Stimulation of wells through mechanical fracturing can be accomplished by a method known as controlled pulse fracturing or high energy gas fracturing. A good description of this method appears in an article by Cuderman, J. F., entitled "High Energy Gas Fracturing Development," Sandia National Laboratories, SAND 83-2137, October 1983. Using this method enables multiple fracturing of a formation or reservoir in a radial manner which increases the possibility of contacting a natural fracture. In the practice of this method, a housing means for containing a propellant is suspended into a wellbore. This housing means is placed downhole next to an oil or hydrocarbonaceous fluid productive interval.
Presently, it is now a common practice to use diesel oil or lease crude as a fluid tamp in a reservoir where contacting the formation with a water-based fluid will cause an undesired loss of permeability. However, neither tamp controls the movement of the wireline and remaining device upon deflagration of the propellant because of the tamp's low viscosity.
The propellant in the housing means or molded body can belong to the modified nitrocellulose or the modified and unmodified nitroamine propellant class. Suitable solid propellants capable of being utilized include a double-based propellant known as M-5. It contains nitroglycerine and nitrocellulose. Another suitable propellant is a composite propellant which contains ammonium perchlorate in a rubberized binder. The composite propellant is known as HXP-100 and is purchasable from the Holex Corporation of Hollister, Calif. M-5 and HXP-100 propellants are disclosed in U.S. Pat. No. 4,039,030 issued to Godfrey et al. which is hereby incorporated by reference.
After placing the propellant means for creating multiple fractures into a housing means and suspending it downhole near the oil or hydrocarbonaceous fluid productive interval, it is ignited. Ignition of the propellant means for creating multiple radial fractures causes the generation of heat and gas pressure. To contain the generated propellant energy within the wellbore and formation, an aggregate stem, generally composed of cement, is placed above the housing means containing the propellant thereby sealing the wellbore. The suspended housing means and ignition means passes through the aggregate stem.
After ignition of the propellant means it is difficult to remove the aggregate stem, which often has to be drilled out. When removing the aggregate stem, the suspension means, generally a cable, and the ignition means, along with remnants of the housing means which previously contained the propellant, frequently fall into the wellbore. This debris may interfere with production of hydrocarbonaceous fluids from the formation. Drilling out the aggregate often damages the wellbore and formation.
Therefore, what is needed is a method to reduce the forces on downhole equipment used during a CPF operation so as to avoid damaging said equipment and formation.